Many technologies are currently being developed to provide the next generation of flat panel displays, projection displays, flexible displays, and micro-displays. Consumers consider flat-panel emissive displays, which emit light in a lambertian behavior, to be the most attractive type of display. Despite the human eye's natural affinity for such emissive displays, liquid crystal displays (LCD's) currently dominate the commercial display market. Because LCD's filter white light, which passes through polarizers, a perceptible variance in image quality is observed with view angle. Furthermore, the vast majority (approximately 90 percent or greater) of light in a LCD never reaches the viewer because of unavoidable absorption in thin film polarizers, color filters, and other optical losses in the LCD. Generally, polarizers transmit only about 40 percent of unpolarized incident light and color filters transmit only about 20 percent to about 30 percent of incident white light. Cold cathode fluorescent lamp (CCFL) backlights, which provide as much as 80 μm/W efficiency, generally result in an LCD efficiency of only a few Im/W.
Alternative flat panel display technologies, such as inorganic electroluminescent displays, organic electroluminescent displays, plasma display panels, and field emission displays, do not require either efficiency-reducing polarizers or heavy color filtering, as do LCD's. Regardless, even these alternative display technologies have comparable or lower efficiency to that of a LCD display panel. Moreover, the manufacture processes for conventional LCD's and these conventional alternative flat panel displays are highly complex.
Electrowetting has been a highly attractive modulation scheme for a variety of optical applications. For example, electrowetting has been used as an optical switch for fiber optics, as an optical shutter or filter for camera and guidance systems, in optical pickup devices, and in optical waveguide materials. Electrowetting has also found applicability in display applications, such as prismatic display devices and for using electrowetting of clear liquids. Electrowetting devices have also been developed for pixelation in emissive waveguide displays.
Opaque electrowetting liquids currently used in conventional reflective displays are severely limited in contrast. Polar colored electrowetting liquids have also been used in conventional transmissive electrowetting displays. However, such polar liquids are susceptible to rapid color-fading with extended light exposure during display operation. Conventional transmissive electrowetting displays are capable of increasing transmission efficiency using a reflector. However, conventional transmissive electrowetting displays suffer from parallax due to the reflector, and to eliminate parallax issues, the backlight must be directional, which severely limits the viewing angle.
A display-capable electrowetting light valve is needed that overcomes these and other deficiencies of conventional display devices.